Is it called "dwell"? Because it's a useful word for an incredibly annoying trend that Google were doing the last few months I used it: whenever I searched for a word I'd used in a previous search they would try really hard to get me the same results as before, including ignoring quoted words and minus-prefixed strings. At that point I just really wanted Google to forget my previous searches, but of course that's impossible. Since I'm interested in more than one thing, using a different search engine is just better.

On a related note, Google seems to be doing something similar with startpage.com searches, I guess because mostly geeks use it. Or else they are somehow getting enough data through startpage.com to identify me.